JP6480845B2 - Conductive resin composition and method for producing the same - Google Patents

Description

  The present invention relates to a conductive resin composition containing carbon nanotubes and excellent in antistatic properties and conductivity, and a method for producing the same.

  A general resin material has low electrical conductivity, and the surface resistivity is generally in the range of 1,014 to 1,016 Ω / □. For this reason, the resin material classified into an insulating material can be used for the product etc. which require electrical insulation. However, in order to use a resin material as a material for forming a molded article, a film, a sheet, or the like that requires antistatic properties, it is necessary to impart conductivity to the resin material. For this reason, many studies have been made so far in order to impart conductivity to the resin material.

  In order to impart conductivity to the resin material (that is, lower surface resistivity), conductive materials such as metal powder, metal fiber, carbon black, graphite, carbon fiber, and carbon nanotube can be dispersed in the resin material. That's fine. However, depending on the mixing composition and mixing / dispersing method, the original mechanical properties of the resin material may be lowered. For this reason, in order to impart conductivity to the resin material, it is important to satisfy both the electrical characteristics and the mechanical characteristics.

  For example, a hydrophobic thermoplastic resin composition containing, for example, a carbon nanotube, a thermoplastic resin, and a specific surfactant has been proposed as a resin material with improved strength and carbon nanotube dispersibility (patent) Reference 1). Also, a method in which carbon nanotubes are brought into contact with a water-soluble polymer or surfactant in an aqueous medium, then mixed with a polymer latex, water is further removed, and then processed into a desired shape, and the reinforcement obtained by this method A polymer has been proposed (Patent Document 2).

  By the way, the crude carbon nanotubes produced by arc discharge method, laser evaporation method, chemical vapor deposition method, etc. contain impurities such as amorphous carbon, metal catalyst fine particles, and graphite nano fine particles. It becomes a footstep when using. As a method for removing impurities from the crude carbon nanotube, for example, a method has been proposed in which the crude carbon nanotube is treated with a cleaning agent containing an alkaline alcohol solution and then the washing treatment with an organic solvent is repeated (Patent Document 3).

JP 2008-231344 A JP-T-2006-517996 JP 2008-290886 A

  In the thermoplastic resin compositions proposed in Patent Documents 1 and 2, it is necessary to increase the amount of conductive material added in order to obtain high conductivity. However, when the addition amount of the conductive material is increased, the original physical properties of the resin such as mechanical properties and molding processability may be impaired. In addition, when the amount of the conductive material added is large, the probability of the conductive material existing on the surface of the obtained resin molded product increases. For this reason, the conductive material that has fallen off from the surface of the molded product due to friction may contaminate the environment and may cause mechanical damage and electrical adverse effects on the electronic device.

  In addition, it is difficult to completely remove impurities from the crude carbon nanotubes by the method proposed in Patent Document 3, and there is a possibility that the cleaning agent used remains.

  The present invention has been made in view of such problems of the prior art, and the problem is that the dispersibility of the carbon nanotubes is good and the amount of carbon nanotubes added is small. The present invention also provides a conductive resin composition that is excellent in conductivity and maintains the original physical properties of a thermoplastic resin such as mechanical strength, and a method for producing the same.

That is, according to the present invention, the following conductive resin composition is provided.
[1] A conductive resin composition containing a thermoplastic resin and carbon nanotubes, wherein the carbon nanotubes are either basic carbon nanotubes or acidic carbon nanotubes (however, basic or acidic functionalities) In addition, when the carbon nanotube is the basic carbon nanotube, the pH adjuster is at least one of a neutral compound and an acidic compound. , and the when the carbon nanotube is the acidic carbon nanotubes, wherein Ri der least one pH adjusting agent is the neutral compounds and basic compounds, the acidic compound is phosphoric acid, organic acids and, Is at least one selected from the group consisting of acidic buffers, Group compound is sodium hydroxide, at least one selected from the group consisting of potassium hydroxide, and basic buffers, the neutral compound is a neutral buffer der Ru conductive resin composition.
[2] The pH of the aqueous dispersion of basic carbon nanotubes at 20 ° C. is 7.1 to 14.5, and the pH of the aqueous dispersion of acidic carbon nanotubes at 2.5 ° C. is 2.5 to 6.9. The conductive resin composition according to [1] .

Moreover, according to this invention, the manufacturing method of the conductive resin composition shown below is provided.
[ 3 ] A method for producing a conductive resin composition according to [1] or [2] , wherein the thermoplastic resin has a particle size of 0.01 to 3 mm, 1 to 100 parts by mass of the thermoplastic resin. 30 parts by mass of carbon nanotubes, 150 to 800 parts by mass of water and / or a hydrophilic organic solvent with respect to 100 parts by mass of the carbon nanotubes, and 0.15 to 27 with respect to 100 parts by mass of the carbon nanotubes A step (A) of obtaining a mixture by mixing 5 parts by mass of a pH adjusting agent, and a step (B) of removing the solvent while kneading the mixture, wherein the carbon nanotube is a basic carbon When the carbon nanotube is the basic carbon nanotube, the pH adjuster A conductive resin composition that is at least one of a neutral compound and an acidic compound, and when the carbon nanotube is the acidic carbon nanotube, the pH adjuster is at least one of the neutral compound and the basic compound Manufacturing method.
[4] the intrinsic viscosity of the thermoplastic resin (IVa (dL / g)) , the intrinsic viscosity of the conductive resin composition (IVb (dL / g)) is, IVa <said to satisfy the relationship of IVb [3] The manufacturing method of the conductive resin composition of description.
[ 5 ] While the acidic compound is an acidic buffer, the acidic compound is used in the state of an acidic buffer having a pH of 2.5 to 6.5 at 25 ° C., and the basic compound is a basic buffer. The manufacturing method of the conductive resin composition as described in said [ 3 ] or [ 4 ] used in the state of the basic buffer whose pH in 7.5-14.5.
[ 6 ] The method for producing a conductive resin composition according to any one of [ 3 ] to [ 5 ], wherein the hydrophilic organic solvent is an alcohol solvent or a glycol solvent.
[ 7 ] The method for producing a conductive resin composition according to any one of [ 3 ] to [ 6 ], wherein in the step (A), a surfactant is further mixed to obtain the mixture.
[8] wherein the amount of surfactant, per 100 parts by weight of the carbon nanotube and the surfactant, conductive according to the more than 40 parts by mass more than 0 parts by mass [7] A method for producing a resin composition.

  According to the present invention, the dispersibility of carbon nanotubes is good, the conductivity is excellent even with a small amount of carbon nanotubes added, and the original physical properties of the thermoplastic resin such as mechanical strength are maintained. The conductive resin composition made and the manufacturing method thereof can be provided.

<Conductive resin composition>
Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. The present inventors paid attention to the pH of the impurities contained in the carbon nanotubes, and examined the influence of the pH of the impurities on the thermoplastic resin. As a result, by adding pH adjusters such as acidic compounds, neutral compounds, and basic compounds together with carbon nanotubes to the thermoplastic resin, the carbon resin maintains the original physical properties of the thermoplastic resin such as mechanical strength. It has been found that a thermoplastic resin composition with improved nanotube dispersibility can be obtained.

  That is, the conductive resin composition of the present invention is a conductive resin composition containing a thermoplastic resin and carbon nanotubes. The conductive resin composition of the present invention further includes a pH adjuster while the carbon nanotube is either a basic carbon nanotube or an acidic carbon nanotube. And when a carbon nanotube is a basic carbon nanotube, a pH adjuster is at least any one of a neutral compound and an acidic compound. On the other hand, when the carbon nanotube is an acidic carbon nanotube, the pH adjuster is at least one of a neutral compound and a basic compound. Hereinafter, the detail of the conductive resin composition of this invention is demonstrated.

(carbon nanotube)
The carbon nanotubes contained in the conductive resin composition of the present invention are either basic carbon nanotubes or acidic carbon nanotubes. The “basic carbon nanotube” in the present specification means one whose pH of the aqueous dispersion at 20 ° C. is usually 7.1 to 14.5. The “acidic carbon nanotube” means that the aqueous dispersion has a pH at 20 ° C. of usually 2.5 to 6.9.

  Even if a carbon nanotube having a pH of 6.9 to 7.1 is blended with a general-purpose thermoplastic resin having good acid / alkali resistance, the intrinsic viscosity (IV value) does not decrease so much. However, when a carbon nanotube having a pH of 6.9 to 7.1 is blended with a polyamide (nylon) resin or a polyacetal resin having poor acid / alkali resistance, the pH of the carbon nanotube is different by only 0.1. It was found that the molecular weight decreased. Therefore, the intrinsic viscosity (IV value) of the resin can be used as an index indicating the influence on the molecular weight of the resin.

  The type of carbon nanotube is not particularly limited, and single-walled carbon nanotubes and multi-walled carbon nanotubes can be used. Among these, multi-walled carbon nanotubes are preferable from the viewpoints of electrical characteristics, mechanical characteristics, and affinity with thermoplastic resins. The number of multi-walled carbon nanotubes is preferably 20 to 50. When the number of multi-walled carbon nanotube layers is within the above range, the conductivity and mechanical properties of the conductive resin composition can be further improved.

  The diameter of the carbon nanotube is preferably 3 to 500 nm, and more preferably 10 to 200 nm. The length of the carbon nanotube is preferably 0.1 to 50 μm, and more preferably 0.5 to 20 μm.

The proportion (based on the number) of 20 to 50 multi-walled carbon nanotubes in the carbon nanotubes contained in the conductive resin composition of the present invention is preferably 50% or more.
The ratio of 20 to 50 multi-walled carbon nanotubes is, for example, the number of fibrous nanotubes present in the field of view by observing an ultrathin section of the conductive resin composition with a transmission electron microscope (magnification: 200,000 times). Can be calculated by counting.

  The cylindrical graphite structure that is characteristic of carbon nanotubes can be confirmed with a high-resolution transmission electron microscope. The graphite layer is so preferable that it can be clearly seen in a straight line with a transmission electron microscope, but the graphite layer may be disordered. A disordered graphite layer may be defined as a carbon nanofiber, but a disordered graphite layer is also included in the concept of carbon nanotubes in the present invention.

  Carbon nanotubes are produced by methods such as laser ablation, arc discharge, thermal CVD, plasma CVD, gas phase, and combustion. The carbon nanotube used in the conductive resin composition of the present invention may be produced by any method. For example, the method of manufacturing by the thermal CVD method using zeolite as a catalyst support and acetylene as a raw material is highly purified and well graphitized without any particular purification, although there is some amorphous carbon coating by thermal decomposition. It is preferable at the point from which a multi-walled carbon nanotube is obtained (Chemical Physics Letters, 303 (1999), p117-124).

  Carbon nanotubes pretreated with a coupling agent can also be used. Examples of the coupling agent include isocyanate compounds, organic silane compounds, organic titanate compounds, organic borane compounds, and epoxy compounds.

  Carbon nanotubes produced by chemical vapor deposition contain impurities such as catalytic metals, amorphous carbon, and graphite nanoparticles. For this reason, in order to obtain high-purity carbon nanotubes, various purifications are performed to remove these impurities. As a purification method, a method of bringing hydrofluoric acid, hydrochloric acid, nitric acid or the like into contact has been proposed. However, the conventional purification method has a problem that the carbon nanotubes form aggregates. In order to solve such problems, it has been proposed to add an additional purification step. Specifically, there are a step in which oxidation treatment or acid treatment in high-temperature air is combined; a step of treatment with an alkaline aqueous solution having a pH of 9 or higher that dissolves the solid catalyst or an acidic aqueous solution of pH 5 or lower. However, in any case, there are concerns about the effect of quality on the carbon nanotube itself as the number of purification steps increases. Further, in the above purification process, it has been difficult to completely remove impurities.

  On the other hand, the conductive resin composition of the present invention reduces the molecular weight of the thermoplastic resin by using a pH adjuster such as an acidic compound or a basic compound according to the characteristics (pH) of the carbon nanotube. While suppressing, the dispersibility of the carbon nanotube is improved and the conductivity is increased.

(PH adjuster)
The conductive resin composition of the present invention contains a pH adjuster. The pH adjuster is a neutral compound, a basic compound, or an acidic compound. As the neutral compound, a neutral buffer or the like whose pH can be maintained in a neutral region can be used. Such a neutral buffer can be used in the state of a buffer solution (neutral buffer solution) dissolved in water. Examples of the neutral buffer include a phosphate buffer and a citrate buffer. As the basic compound, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate (including hydrate), ammonia and the like can be used. These basic compounds can be used singly or in combination of two or more. In addition, a basic compound having a low melting point such as sodium hydrogen carbonate, disodium hydrogen phosphate, or calcium hydrogen phosphate dihydrate can be used. Of these, sodium hydroxide and potassium hydroxide are preferred in view of solubility, foamability, workability such as odor, and the like.

  As the types of acidic compounds, inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and hydrofluoric acid; organic acids such as acetic acid, citric acid, oxalic acid, and pyrrolidone carboxylic acid can be used. These acidic compounds can be used alone or in combination of two or more. In addition, when using carbon nanotubes with a large amount of remaining metal catalyst, hydrochloric acid is preferably used as the acidic compound. On the other hand, when using thermoplastic resins that are weak against acids such as polyamide (nylon) resins and polyacetal resins, it is preferable to use phosphoric acid, which has a small influence on these resins, as the acidic compound.

  Moreover, as an acidic compound, buffering agents, such as an acidic buffering agent which is a combination of a weak acid and its conjugate base, can be used. On the other hand, as the basic compound, a buffer such as a basic buffer that is a combination of a weak base and its conjugate acid can be used. Such a buffer can be used in the state of a buffer solution (acid buffer solution, basic buffer solution) dissolved in water.

(Thermoplastic resin)
Examples of the thermoplastic resin that can be used include olefin resins, nylon resins, polyamide resins, polycarbonate resins, polysulfone resins, polyester resins, and cellulose resins such as triacetylated cellulose and diacetylated cellulose. .

  Specific examples of the polyamide resin include polyamide 6 (PA6, ring-opening polymer of ε-caprolactam), polyamide 66 (PA66, polyhexamethylene adipamide), and polyamide 11 (PA11, undecane lactam). Polyamide), polyamide 12 (PA12, polyamide obtained by ring-opening polycondensation of lauryl lactam) and the like.

  As the thermoplastic resin, an olefin resin is preferable because of the advantage that the reinforcing effect of the conductive resin composition can be sufficiently obtained and the advantage that it is inexpensive. Examples of the olefin resin include general-purpose resins such as polyethylene resin, polypropylene resin, vinyl chloride resin, styrene resin, (meth) acrylic resin, and vinyl ether resin. These thermoplastic resins can be used singly or in combination of two or more. Among olefin resins, in terms of reinforcement effect and cost, high density polyethylene (HDPE), low density polyethylene (LDPE), polyethylene resins such as biopolyethylene (PE), polypropylene resin (PP), vinyl chloride resin, Styrene resin, (meth) acrylic resin, vinyl ether resin and the like are preferable.

  Among the highly versatile olefin-based resins, they are inexpensive and excellent in processability, and have characteristics such as heat resistance and chemical resistance, and are widely used in various industrial parts and home appliances. Polypropylene, polyethylene and polyester are preferred.

  Specific examples of polypropylene include homopolypropylene, random propylene copolymer, block propylene copolymer, ethylene propylene copolymer, polypropylene obtained using a metallocene catalyst, maleic anhydride modified polypropylene, glycidyl (meth) acrylate modified polypropylene. And modified polypropylene resins such as 2-hydroxyethyl (meth) acrylate-modified polypropylene, and olefin elastomers.

  Specific examples of polyethylene include low density polyethylene, high density polyethylene, ultra low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polyethylene obtained using a metallocene catalyst, glycidyl (meth) acrylate modified polyethylene, 2- Examples thereof include modified polyethylene resins such as hydroxyethyl (meth) acrylate-modified polyethylene, cyclic polyethylene, and maleic anhydride-modified polyethylene.

  Specific examples of polyesters include polyglycolic acid, polylactic acid, poly (3-hydroxybutyric acid), poly (4-hydroxybutyric acid), polycaprolactone and other ring-opening polyaddition aliphatic polyesters, polyester carbonate, polyethylene terephthalate, poly Butylene terephthalate, copolymer of polyethylene terephthalate and polyethylene isophthalate, polyethylene succinate, polybutylene succinate, polyhexamethylene succinate, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polyethylene oxalate, polybutylene oxalate And polycondensation reaction type aliphatic polyester such as polyhexamethylene oxalate, polyethylene sebacate, polybutylene sebacate and the like.Among these, polyethylene terephthalate is preferable from the viewpoint of recyclability.

  The intrinsic viscosity (IV value) of the polyester is preferably 0.5 dL / g or more in consideration of the impact resistance of the obtained conductive resin composition. Furthermore, considering the moldability of the resulting conductive resin composition, the intrinsic viscosity (IV value) of the polyester is preferably 0.9 dL / g or less, and more preferably 0.8 dL / g or less. As described above, the intrinsic viscosity (IV value) of the polyester is preferably 0.5 to 0.9 dL / g, and more preferably 0.5 to 0.7 dL / g.

  In the conductive resin composition of the present invention, a plasticizer, a polymer dispersant, an ultraviolet absorber, an antioxidant, a light stabilizer, a lubricant, and a nucleating agent are included in the range that does not impair the effects of the present invention. Various additives such as fillers, pigments and flame retardants can be contained. Among these, it is preferable to use a polymer dispersant because the dispersibility of the carbon nanotubes can be further improved. The polymer dispersant is preferably a block copolymer composed of a methacrylate monomer or a methacrylic acid monomer and synthesized by a living radical polymerization method.

  If the conductive resin composition of the present invention is molded by a known molding method, a molded product having a desired shape can be obtained. Examples of the molding method include an injection molding method, an extrusion molding method, and a press molding method. Also, known composite molding techniques such as foam molding, two-color molding, insert molding, outsert molding, and in-mold molding can be applied. Examples of the molded product include injection molded products, sheets, unstretched films, stretched films, extruded products such as round bars and deformed extruded products, fibers, filaments, and the like. In addition, the conductive resin composition of the present invention can be used as a suspension as an adhesive, paste, paint, or coating agent.

<Method for producing conductive resin composition>
The method for producing a conductive resin composition of the present invention includes a step (A) of mixing each component to obtain a mixture (hereinafter also referred to as “mixing and dispersing step”), and removing the solvent while kneading the obtained mixture. (B) (hereinafter also referred to as “kneading / solvent removal step”). The details will be described below.

(Process (A) (mixing and dispersing process))
In the mixing and dispersing step, a thermoplastic resin having a particle size of 0.01 to 3 mm, 1 to 30 parts by mass of carbon nanotubes with respect to 100 parts by mass of the thermoplastic resin, and 150 to 800 parts by mass of water with respect to 100 parts by mass of the carbon nanotubes. In addition, 0.15 to 27.5 parts by mass of a pH adjuster is mixed with 100 parts by mass of carbon nanotubes and at least one of the hydrophilic organic solvent and carbon nanotubes to obtain a mixture.

The order of mixing the components is not particularly limited, but for example, the following mixing methods (a) to (c) are preferable.
(A) After mixing the carbon nanotube and the thermoplastic resin, a solvent and a pH adjuster are added and further mixed.
(B) After mixing the carbon nanotube, the pH adjuster, and the solvent, the thermoplastic resin is added and further mixed.
(C) A carbon nanotube, a pH adjuster, a solvent, and a thermoplastic resin are mixed together.
Among the above mixing methods (a) to (c), the mixing method (a) is preferable from the viewpoint of easy mixing and high dispersibility.

  In the mixing and dispersing step, for example, a dispersing machine such as a Henschel mixer, a super mixer, an ultrasonic homogenizer, a spiral mixer, a planetary mixer, a disperser, or a hybrid mixer is preferably used. Two or more dispersers may be used in combination. Among them, it is preferable to use a Henschel mixer, a super mixer, or an ultrasonic homogenizer from the viewpoint of suppressing the dispersibility of the carbon nanotubes in the thermoplastic resin and the damage of the carbon nanotubes. Furthermore, it may be further dispersed by using a ball mill, a vibration mill, a sand mill, a roll mill, or the like as required, as long as the carbon nanotubes are not damaged.

  As a thermoplastic resin, the thing of the powder form or pellet shape whose particle size is 0.01-3 mm is used. By using the thermoplastic resin having the above particle diameter, the carbon nanotubes are easily loosened by the thermoplastic resin, and kneading is facilitated. The amount of the carbon nanotube is 1 to 30 parts by mass with respect to 100 parts by mass of the thermoplastic resin. When the amount of the carbon nanotube is 1 part by mass or more with respect to 100 parts by mass of the thermoplastic resin, a conductive resin composition having good conductivity can be obtained. On the other hand, when the amount of the carbon nanotube is 30 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin, a conductive resin composition in which the original physical properties of the thermoplastic resin are maintained can be obtained.

  As the solvent, it is preferable to use a solvent that has a boiling point that easily evaporates in the subsequent kneading / solvent removal step and hardly remains in the obtained conductive resin composition. As the solvent, at least one of water and a hydrophilic organic solvent is used in consideration of the influence on the working environment, cost, handling properties, and the like. As the hydrophilic organic solvent, an alcohol solvent or a glycol solvent can be used, and ethanol is particularly preferable. Moreover, you may use water and alcohol together. The amount of the solvent may be not less than the amount capable of dispersing the carbon nanotubes and not more than the amount removable by kneading. Specifically, 150 to 800 parts by mass of solvent is used with respect to 100 parts by mass of the carbon nanotubes.

  When the carbon nanotube is a basic carbon nanotube, at least one of a neutral compound and an acidic compound is used as a pH adjuster. On the other hand, when the carbon nanotube is an acidic carbon nanotube, at least one of a neutral compound and a basic compound is used as a pH adjuster. And the quantity of a pH adjuster shall be 0.15-27.5 mass parts with respect to 100 mass parts of carbon nanotubes.

  The pH adjuster can be used in the form of a solution dissolved in a solvent such as water. Moreover, when using an acidic buffer as an acidic compound, it is preferable to use in the state of the acidic buffer whose pH in 25 degreeC is 2.5-6.5. On the other hand, when a basic buffer is used as the basic compound, it is preferably used in the state of a basic buffer having a pH of 7.5 to 14.5 at 25 ° C. Furthermore, when using a neutral buffer as a neutral compound, it is preferable to use it in the state of the neutral buffer whose pH in 25 degreeC exceeds 6.5 and is less than 7.5. Buffers include phosphate buffer (pH 5.5 to 8.2), acetate buffer (pH 3.4 to 5.8), citrate buffer (pH 2.5 to 8), other acidic buffers ( pH 2 to 6.9), other basic buffers (pH 7.1 to 14.5), deionized water, and the like can be used. In view of the influence on the thermoplastic resin and the like, a phosphate buffer or a citrate buffer is preferable.

  In the mixing and dispersing step, it is preferable to further mix the surfactant to obtain a mixture. By adding the surfactant, the solvent containing the surfactant can easily penetrate into the aggregate of the carbon nanotubes, and the effect of loosening the carbon nanotubes can be improved. As the surfactant, ionic surfactants such as anionic surfactants, cationic surfactants, and amphoteric surfactants; nonionic surfactants can be used. Examples of the anionic surfactant include sulfate type, phosphate type and sulfonic acid type surfactants. Examples of the cationic surfactant include quaternary ammonium salt type surfactants. Examples of the amphoteric surfactant include alkyl betaine type, amide betaine type, and amine oxide type surfactants. Moreover, surfactants, such as fatty acid ester and sorbitan fatty acid ester, can be mentioned as nonionic surfactant.

  The amount of the surfactant may be in a range that does not deteriorate the physical properties of the obtained conductive resin composition. Specifically, the amount of the surfactant is preferably more than 0 parts by mass and 40 parts by mass or less with respect to 100 parts by mass in total of the carbon nanotube and the surfactant.

  According to the method for producing a conductive resin composition of the present invention, the carbon nanotubes are dispersed in a good state without impairing the physical properties such as mechanical strength inherent to the thermoplastic resin, and the conductive resin composition having excellent conductivity. Can be manufactured. And the reduction of the mechanical strength etc. of the thermoplastic resin is grasped by comparing the intrinsic viscosity (IVa) of the thermoplastic resin as a raw material with the intrinsic viscosity (IVb) of the obtained conductive resin composition. Can do. In the method for producing a conductive resin composition of the present invention, the intrinsic viscosity (IVa (dL / g)) of the thermoplastic resin and the intrinsic viscosity (IVb (dL / g)) of the conductive resin composition are preferably The relationship IVa <IVb is satisfied. For this reason, according to this invention, the conductive resin composition with which physical properties, such as a mechanical strength inherent in a thermoplastic resin, were maintained can be manufactured.

(Process (B) (kneading / solvent removal process))
In the kneading / solvent removing step, the solvent in the mixture is removed while kneading the mixture obtained in the mixing and dispersing step. Thereafter, a pellet-like or flake-like conductive resin composition can be obtained by granulating as necessary. In addition, after mixing raw material resin with a predetermined ratio with the high concentration goods (masterbatch) with much carbon nanotube content, you may granulate using kneading machines, such as an extruder and a roll.

  For the kneading of the mixture, for example, an extruder, a kneader mixer, a Banbury mixer, or the like can be used. What is necessary is just to set process temperature and a pressure suitably according to the kind etc. of a thermoplastic resin and a solvent. However, in order to remove a solvent, it is preferable to process at high temperature, and specifically, it is preferable to process at 100-370 degreeC.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.

<Measurement of pH of aqueous dispersion of carbon nanotube>
After calibrating the pH measuring device with a standard solution conforming to the USA standard, 4 g of carbon nanotubes were added to 60 g of ion-exchanged water, and the mixture was treated with an ultrasonic cleaner for 2 minutes to prepare an aqueous dispersion. Then, the pH of the prepared aqueous dispersion at 20 ° C. was measured. In addition, as a pH measuring device, a trade name “LAQUA act” (manufactured by Horiba, Ltd.) was used. By measuring the pH of the aqueous dispersion of carbon nanotubes, the type and amount of the pH adjusting agent to be used can be set.

In addition, the measurement result of pH of the aqueous dispersion of carbon nanotubes used in the following examples and comparative examples is as follows.
-PH of aqueous dispersion of trade name "AMC" (manufactured by Ube Industries): 10.5

<Manufacture of conductive resin composition>
Example 1
Mix 4 parts of carbon nanotube (trade name “AMC”, manufactured by Ube Industries), 96 parts of polyethylene terephthalate (trade name “Unipet BK2180”, manufactured by Nihon Unipet Co., Ltd.) with a particle size of 0.05 to 1.1 mm. And stirred and mixed at 25 ° C. for 3 minutes. 6 parts of 0.28% phosphoric acid aqueous solution prepared by diluting phosphoric acid (manufactured by Kokusan Kagaku) with water was added, and the mixture was stirred and mixed at 25 ° C. for 2 minutes to obtain a mixture. Using a twin screw extruder (trade name “TEX30”, manufactured by Nippon Steel Works), the solvent (water) was removed by evaporation from the vent of the twin screw extruder while the resulting mixture was melt kneaded at a processing temperature of 280 ° C. Thus, a pellet-shaped conductive resin composition was obtained.

(Example 2)
A conductive resin composition was obtained in the same manner as in Example 1 except that 0.1 part of a surfactant (trade name “Hosta Pure SAS 93”, manufactured by Clariant) was added along with the phosphoric acid aqueous solution.

(Examples 3 to 6)
Except having used the phosphoric acid aqueous solution of the density | concentration shown in Table 1, it carried out similarly to the above-mentioned Example 2, and obtained the conductive resin composition.

(Example 7)
A 0.1 mol / L phosphate buffer solution (pH 7.0 (25 ° C.)) was prepared using sodium dihydrogen phosphate (manufactured by Kokusan Chemical Co., Ltd.) and disodium hydrogen phosphate (manufactured by Wako Pure Chemical Industries, Ltd.). . A conductive resin composition was obtained in the same manner as in Example 2 except that the prepared phosphate buffer was used instead of the phosphoric acid aqueous solution.

(Examples 8 to 13)
A conductive resin composition was obtained in the same manner as in Example 7 except that the phosphate buffer solution having the pH, concentration and amount shown in Table 1 was used.

(Comparative Example 1)
A conductive resin composition was obtained in the same manner as in Example 1 except that 6 parts of water was used instead of the phosphoric acid aqueous solution.

(Comparative Example 2)
A conductive resin composition was obtained in the same manner as in Comparative Example 1 except that water was not used.

(Reference Example A)
The polyethylene terephthalate used in the examples was referred to as Reference Example A.

  Table 1 summarizes the compositions of Examples 1 to 13, Comparative Examples 1 and 2, and Reference Example A.

<Evaluation>
(Surface resistivity)
Using an extruder equipped with a belt die (trade name “NV-20”, manufactured by Mars Seiki Co., Ltd.), the obtained conductive resin composition was molded, and an evaluation sheet having a thickness of about 0.1 mm and a width of 50 mm Manufactured. Then, using a low resistivity meter (trade name “Loresta GP”, manufactured by Mitsubishi Chemical Corporation) and a high resistivity meter (trade name “Hiresta UP”, manufactured by Mitsubishi Chemical Corporation), the surface resistivity of the manufactured evaluation sheet (Ω / □) was measured. The results are shown in Table 2.

(Intrinsic viscosity (IV value))
Based on JIS K7390: 2003, the intrinsic viscosity (IV value) of the resin composition (resin) was measured by the method shown below. The resin composition was put into a solvent (phenol / tetrachloroethane = 50/50 (mass ratio)) and heated at 120 ° C. for 10 minutes to dissolve the resin. After cooling to room temperature, a sample solution having a resin concentration of 0.2 g / dL was obtained. Using a capillary viscometer, the flow time of the sample solution and the flow time of the solvent alone were measured, and the intrinsic viscosity (IV value: dL / g) was calculated from the time ratio using the Huggins formula. The Huggins constant was set to 0.33. The results are shown in Table 2.

(Distributed state)
The conductive resin composition was sheet pressed to obtain a sheet having a thickness of about 20 μm. And the dispersion state of the carbon nanotube in the sheet | seat obtained with the optical microscope was observed, and the dispersion state of the carbon nanotube was evaluated according to the evaluation criteria shown below. The results are shown in Table 2.
[Evaluation criteria for distributed state]:
“Comparative Example 2” was set to “E”, and the evaluation was relatively made in five stages of “A”, “B”, “C”, “D”, and “E” in order of good dispersion state.

(Impact strength)
The conductive resin composition was molded using an extruder to obtain a pellet. According to ASTM D256, after forming a dumbbell with an injection molding machine, it was notched and the impact strength was measured with an impact tester. And impact strength was evaluated according to the evaluation criteria shown below. The results are shown in Table 2.
[Evaluation criteria for impact strength]:
“Reference Example A” is “S” and “Comparative Example 1” is “E”, and “S”, “A”, “B”, “C”, “D”, “E” in order of good impact strength. The 6 grades were relatively evaluated.

  Since the conductive resin composition of the present invention has high conductivity, maintains the original physical properties of the resin, and is excellent in processability, it is a molded product requiring antistatic properties such as a film or a sheet. It is useful as a material or as a material such as a guide roller, a transport roll, an adhesive, a paste, a paint, and a coating agent in a production line such as a metal foil.

Claims (8)

A conductive resin composition containing a thermoplastic resin and carbon nanotubes,
The carbon nanotube is either a basic carbon nanotube or an acidic carbon nanotube (however, excluding a carbon nanotube modified with a basic or acidic functional group) , and further contains a pH adjuster,
When the carbon nanotube is the basic carbon nanotube, the pH adjuster is at least one of a neutral compound and an acidic compound,
When the carbon nanotube is the acidic carbon nanotubes state, and are at least one of the pH adjusting agent is the neutral compound and a basic compound,
The acidic compound is at least one selected from the group consisting of phosphoric acid, organic acid, and acidic buffer;
The basic compound is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and a basic buffer;
The neutral compound is a neutral buffer der Ru conductive resin composition. PH of the aqueous dispersion of the basic carbon nanotube at 20 ° C. is 7.1 to 14.5,
2. The conductive resin composition according to claim 1, wherein the aqueous dispersion of acidic carbon nanotubes has a pH at 20 ° C. of 2.5 to 6.9. It is a manufacturing method of the conductive resin composition according to claim 1 or 2 ,
Thermoplastic resin having a particle size of 0.01 to 3 mm, 1 to 30 parts by mass of carbon nanotubes with respect to 100 parts by mass of the thermoplastic resin, 150 to 800 parts by mass of water and hydrophilicity with respect to 100 parts by mass of the carbon nanotubes A step (A) of obtaining a mixture by mixing 0.15 to 27.5 parts by mass of a pH adjusting agent with respect to 100 parts by mass of the organic nanotube and at least one of organic solvents;
And (B) removing the solvent while kneading the mixture,
The carbon nanotube is either a basic carbon nanotube or an acidic carbon nanotube,
When the carbon nanotube is the basic carbon nanotube, the pH adjuster is at least one of a neutral compound and an acidic compound,
When the carbon nanotube is the acidic carbon nanotube, the method for producing a conductive resin composition, wherein the pH adjuster is at least one of the neutral compound and the basic compound. The conductive viscosity according to claim 3 , wherein the intrinsic viscosity (IVa (dL / g)) of the thermoplastic resin and the intrinsic viscosity (IVb (dL / g)) of the conductive resin composition satisfy a relationship of IVa <IVb. For producing a conductive resin composition. The acidic compound is an acidic buffer, and is used in the state of an acidic buffer having a pH of 2.5 to 6.5 at 25 ° C.
The conductive resin composition according to claim 3 or 4 , wherein the basic compound is a basic buffer and is used in a state of a basic buffer having a pH of 7.5 to 14.5 at 25 ° C. Method. The method for producing a conductive resin composition according to any one of claims 3 to 5 , wherein the hydrophilic organic solvent is an alcohol solvent or a glycol solvent. Method for producing, in the step (A), a conductive resin composition according to any one of claims 3-6 of a surfactant further mixed to obtain the mixture. The amount of the surfactant, of the the total 100 parts by weight of carbon nanotubes and the surfactant, the conductive resin composition according to claim 7 or less 40 parts by mass more than 0 parts by weight Production method.